Pretreatment of paper pulp with ketene dimer in improving sizeability



United States Patent poration of Delaware I No Drawing. Filed Oct. 23, 1961, Ser. No. 147,050

6 Claims. (Cl. 162158) This invention relates to improvements in the sizing of paper and more particularly to the pretreatment of paper and/ or paper pulp with aqueousketene dimer emulsions to improve its sizeability when treated subsequently with other sizing agents.

A principal object of the invention is the provision of avprocess for the treatment of pulp and paper to facilitate and improve the sizing thereof with other sizing agents.

Another object of the invention is the provision of an improved process for the preparation of sized paper.

In accordance with the invention, it has been found that when paper or paper pulp is pretreated with a relatively small amount of a higher organic ketene dimer emulsion, under conditions such that the ketene dimer becomes attached to the fibers, and the paper or pulp then processed and sized in the usual manner, such pretreated paper or pulp is much harder sized than an untreated paper or pulp similarly processed and sized.

The pretreatment can be carried out. in any manner which will cause the pretreating 'material t o become permanently anchored or attached to the pulp fibers. Thus, for example, an aqueous ketene dimer emulsion can be sprayed on the fibers and the fibers then dried under conditions of temperature and time sufiicient to cause the aforesaid anchoring or attachment of the pretreating material to the fibers. In an alternative procedure, the aqueous ketene dimer emulsion can be added to an aqueous pulp suspension, the pulp formed into sheets or mats, and dried under conditions of temperature and time suflicient to cause the materialto become permanently anchored or attached to the fibers, and the pulp sheets or mats subsequently defibered preparatory to refining and converting into paper in the usual manner. After the pulp has been pretreated as indicated, it can be processed into sized paper in the usual manner, the sizing material being added internally at any suitable point prior to sheet formation or applied externally to the sheet after it has been formed. I

Having described the invention generally, the following examples are given to illustrate specific embodiments thereof.

EXAMPLES 1-7 Abitibi bleached sulfite pulp was defibered in a Noble and Wood cycle beater. This pulp was then made into handsheets with half of the pulp being treated with an aqueous emulsion containing 1.5% of a mixed hexadecyltetradecyl ketene dimer and 3.0% of a cationic starch andthe other half of the pulp being made into handsheets with no treatment with the aqueous ketene dimer emulsion. The alkyl ketene dimer emulsion was added to the aliquot at the 0.1% level (based on dry alkyl ketene dimer). The entire papermaking system was adjusted to pH 7.5 using NaHCO Handsheets prepared were dried on a drum drier at C. and then placed in C. forced draft oven for fifteen minutes.

On the following day these handsheets were repulped in a Valley type beater with the following data being obtained:

Handsheets containing the alkyl ketene dimer were soaked for 69 minutes before being defibered. It required double the time to charge this pulp to the beater as compared with the handsheets which had not been treated with the alkyl ketene dimer emulsion.

A series of forty-pound handsheets was prepared from the reworked pulp. Sizing was carried out at the 1.0, 2.0 and 3.0% sizing levels using a fortified rosin paste size. The papermaking procedure utilized consisted of adding the appropriate volume of dilute size emulsion to 2,000 g. of 2.5% pulp, adjusting the pH with alum, and diluting the pulp in the proportioner to 0.25%. Aliquots of 1,000 ml. where then withdrawn and added to about 9 l. of Water in the sheet mold. The 8 x 8 inch sheets were squeezed between felts and dried on a steamheated drum drier at about 240 F.

The handsheets were tested for basis weight and ink photometer (Hercules) using both standard feather ink and water plus a dye solution The average testing data obtained for duplicate runs are shown in Table 1.

Table 1 WITHOUT ALKYL KETENE DIMER PRETREATMENT Ink Photometer 85% WITH 0.1% ALKYL KETENE DIMER PRETREATMENT 0% Fortified Rosin Size 39. 4 3 8 1.0% Fortified Rosin Size 40. 1 204 420 2.0% Fortified Rosin Size 40. 1 251 410 .0% Fortified Rosin Size 40. 6 318 708 3 EXAMPLE 841 A series of forty-pound handsheets was prepared from untreated handsheets for ink photometer only. The results obtained on duplicate runs are shown in Table 2.

Beating Time S-R pH After (Minutes) Freeness Beating Untreated 12 740 6. 35 Treated 12 740 6. 30

Sizing was carried out according to the following furnish list:

( 1) 0.1% dimer (added as the above-described ketene dimer emulsion)pH 7.5.

(2) 0.2% dimer (added as the above-described ketene dimer emulsion)pH 7.5. The pretreated handsheets containing ketene dimer were tested for basis weight and ink photometer and the EXAMPLES 12 27 Approximately fifty 8 x 6 inch sheets of waterleaf paper prepared from St. Regis bleached kraft pulp were tub-sized in an aqueous emulsion containing about 0.0735% of a mixed hexadecyl-tetradecyl ketene dimer. Wet pickup was about 80% indicating the application of about 0.06% of the ketene dimer. The sheets were drum dried seconds at 240 F. and then cured 15 minutes at 100 C. Photometer sizing with 20% lactic acid ink to 85% reflectance averaged 66 seconds for four samples from one sheet.

The remaining sheets (treated as above) were extracted thoroughly with a 50:50 (by volume) blend of methanol and methylene chloride. The extracted sheets were air dried, and one sheet was tested as above. The average photometer sizing was 24 seconds.

Various materials (350 ml.). The tub-sizing technique of xylene applied to untreated waterleaf gave a pickup of about 30%. Therefore, the tub-sizing of untreated waterleaf and the extracted, ketene dimer treated sheets in the above solutions should have applied about 0.5% of the various sizing agents. This assumes (reasonably) that there was no substantivity of the agents to the paper. The tubsized sheets were drum dried 60 seconds at 240 F. Table 3 shows the materials used and photometer sizing values obtained on waterleaf and extracted, ketene dimer treated paper with 20% lactic acid ink. The end point was 85% reflectance. The values given are averages of four determinations.

(5 g.) were dissolved in xylene- Table 3 Example Sizing Agent M.P., C. Untreated Aquapel N 0. I Treated Milxieg hexadecyl-tetradecyl ketene 4550 1 380 2 670 er. Hy lrolyzed mixed hexadecyl-tetradecyl -70 0 985 ketene dimer. Crude scale wax -50 14 560 Refined paraflin wax -60 53 665 Terpene resin (M.P B 40 8 410 Terpene resin (M.P. C.) 3 55 46 810 Terpene resin (M.P.E C.).- 3 70 87 590 Terpene resin (M.P.45 C.)-.--. 8 115 0 540 Glycerol ester of hydrogenated rosin. 4 0 390 Dehydroabietyl nitrile- 88 0 150 Rosin 4 90 0 410 Glycerol ester of polymerized rosin 4 114 58 575 Pentaerythritol ester of hydrogenated 4 106 86 625 ros n. Modified pentaerythritol ester of rosin.-- 4 21 705 Pentaerythritol ester of rosin 4 158 215 660 Pentaerythritol ester of modified rosin... 4 193 0 565 4 Drop softening point indicated in H tamed at the Research Center of Here ercules Powder Company Trade Literature or obules Powder Company.

In accordance with the invention, paper or paper pulp is pretreated with an aqueous ketene dimer emulsion to improve sizeability and the sizing agent then applied in the usual manner. The pretreatment is carried out under conditions which will cause the pretreating material to become permanently attached or aifixed to the fibers. This will usually involve drying and/or heating the fibers after application thereto of the treating material at suitable temperatures, i.e., from about 100 C. to about 125 C. and for a sufficient time, i.e., from about 1 minute to about 30 minutes, to accomplish the desired objective. It will be appreciated that these ranges of temperature and time are not critical and are merely given as illustrative.

The pretreatment contemplated herein can be carried out in a number of ways. For example, where surface sizing, as with an aqueous wax emulsion, is contemplated, the pretreating material can be added to the aqueous pulp suspension prior to sheet formation. After the sheet is formed and dried, so that the pretreating material is attached thereto, the sheet can then be treated with the wax emulsion in any suitable manner, as by dipping, spraying, or the like. In an alternative method, the pretreatment can be applied to the formed sheets, the sheets dried and heated, and then treated with the sizing agent. In another alternative method where the size is applied internally prior to sheet formation, the pretreatment can be applied to the pulp and the treated pulp then processed into paper in the usual manner.

In carrying out the pretreatment, as above described, the aqueous ketene dimer emulsion can be added to an aqueous suspension of the pulp followed by drying and heating. If desired, the treated pulp can be formed into a sheet or web, dried by heating, and then subsequently defibered preparatory to introduction into the papermaking system. In cases where the pretreating material is applied to the formed paper sheet, this can be done by spraying the sheet with the aqueous ketene dimer emulsion or by immersing the sheet in the aqueous ketene dimer emulsion. The amount of pretreating material utilized will vary depending upon the particular ketene dimer used, the type of pulp, the manner of pretreatment, and so on. In general, however, the amount will vary from about 0.01% to 5% by weight, based on the weight of dry fiber.

The ketene dimers which are particularly useful in the process of the present invention are dimers having the formula [RCH=C=O] where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl, and alkaryl. In naming ketene dimers, the radical R is named followed by ketene dimer. Thus, phenyl ketene dimer is:

benzyl ketene dimer is:

and decyl ketene dimer is: [C H CH=(:O] Representative ketene dimers whose emulsions may be used in the process of the instant invention include octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, phenyl, benzyl, ,B-naphthyl and cyclohexyl ketene dimers, as Well as the ketene dimers prepared from montanic acid, naphthanic acid, A -decylenic acid, A -dodecylenic acid, palmitoleic acid, oleic acid, ricinoleic acid, petroselinic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, licanic acid, parinaric acid, tariric acid, gadoleic acid, arachidonic acid, cetoleic acid, erucic acid and selacholeic acid, as well as ketene dimers prepared from naturally occurring mixtures of fatty acids, such as those mixtures found in coconut oil, babassu oil, palm kernel oil, palm oil, olive oil, peanut oil, rape oil, beef tallow, lard (leaf) and whale blubber. Mixtures of any of the above-named fatty acids with each other may also be used.

The pretreatment herein described can be used in conjunction with any of the usual sizing agents for paper such as rosin size, aqueous wax emulsions, alkyl ketene dimers, and so on. In fact, the pretreatment of the invention appears to improve sizeability of paper pulp regardless of the type of sizing material used. While the reasons for this are not entirely understood, it is believed that in the case of paper or pulp being treated with a sizing agent such as wax or rosin, the pretreating chem ical acts as a type of primer that promotes better distribution and adhesion of the sizing material to the substrate. For sizing agents such as alkyl ketene dimer that react with the substrate, it can be visualized that the pretreatment of pulp or paper places on the fiber a closely held material which has more reaction sites for the alkyl ketene dimer than ,did the original fiber. Regardless of the theory involved, and applicant does not intend to be bound by any particular theory, it has been found as a practical matter that the pretreatment herein involved increases sizeability of the pulp or paper and that a much greater degree of sizing is obtained with pulp or paper so treated than is obtained with pulp or paper which has not received such a pretreatment.

Sizing can be carried out by internal application, as by adding the sizing agent preferably in the form of an aqueous emulsion or dispersion to the beater of a papermaking system, or by surface application, as by tubsizing, spray application or the like. The amount of sizing agent applied to the fibers will vary depending upon a number of factors and, in general, will be from about 0.05% to about 10% by weight, based on the weight of fibers.

As used here-in, the expression permanently anchored or attached to the fibers means that the material cannot be removed from the fibers with water or solvents. This attachment or anchoring appears to result from the reaction of the material with the fibers and/or with itself, such reaction being brought about by the drying of the pulp or paper under suitable conditions after the pretreating material has been applied thereto.

What I claim and desire to protect by Letters Patent is:

1. A method of sizing paper which comprises pretreating paper fibers with from about 0.01% to about 5% by weight, based on the weight of dry fibers, of a higher organic ketene dimer having the formula [RCH= C'=O'] where R is a radical selected from the group consisting of alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl, and alkaryl, said ketene dimer being in the form of an aqueous emulsion, drying the treated fibers under conditions to cause the higher organic ketene dimer to become attached thereto, applying a sizing material selected from the group consisting of rosin size, wax size and ketene dimer size to the thus treated fibers, and drying and heating the thus treated fibers to develop sizing.

2. A method of preparing sized paper which comprises pretreating paper pulp with from about 0.01% to about 5% by weight, based on the weight of dry fibers, of a higher organic ketene dimer having the formula [RCH=C=O] where R is a radical selected from the group consisting of alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl, and alkaryl, said ketene dimer being in the form of an aqueous emulsion, drying and heating the pulp to cause the higher organic ketene dimer to become attached to the fibers thereof, forming an aqueous suspension of the pulp, adding thereto from about 0.05% to about 10% of a sizing agent selected from the group consisting of rosin size, wax size and ketene dimer size forming the pulp into a sheet, and drying the sheet.

3. A method of sizing paper which comprises applying thereto from about 0.01% to about 5% by weight,

7 based on the weight of dry fibers, of a higher organic ketene dimer having the formula [RCH=C=O] where R is a radical selected from the group consisting of alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl, and alkaryl, said ketene dimer being in the form of an aqueous emulsion, drying and heating the paper to cause the higher organic ketene dimer to become attached thereto, applying a sizing material selected from the group consisting of rosin size, wax size and ketene dimer size to the thus treated paper, and drying and heatingthe paper to develop the s1z1ng.

4. A method in accordance with claim 2 wherein the pretreating material is an alkyl ketene dimer and the size is rosin size.

5. A method in accordance with claim 2 wherein both the pretreating material and size are alkyl ketene dimers.

6. A sized paper produced in accordance with the method of claim 1.

References Cited by the Examiner' UNITED STATES PATENTS i 2/43 Toland et a1. 3/57 Osberg 162]158 6/58 Grunfest et a1. 162168 7/59 Callear et al.

2 /60 Keim 162164 10/61 Schur 162158 1/62 Pattiloch 162-182 8/62 Arlt 162 -158 11/62 Herdle et a1. 162-135 FOREIGN PATENTS 9/46 Great Britain. 6/54 Great Britain. 11/5 8 Great Britain.

lDONALL H. SYLVESTER, Primary Examiner.

RICHARD D. NEVINS, MORRIS o. WOLK,

Examiners. 

1. A METHOD OF SIZING PAPER WHICH COMPRISES PRETREATING PAPER FIBERS WITH FROM ABOUT 0.01% TO ABOUT 5% BY WEIGHT, BASED ON THE WEIGHT OF DRY FIBERS, OF A HIGHER ORGANIC KETENE DIMER HAVING THE FORMULA (RCH= C=O)2 WHERE R IS A RADICAL SELECTED FROM THE GROUP CONSISTING OF ALKYL HAVING AT LEAST 8 CARBON ATOMS, CYCLOALKYL HAVING AT LEAST 6 CARBON ATOMS, ARYL, ARALKYL, AND ALKARYL, SAID KETENE DIMER BEING IN THE FORM OF AN AQUEOUS EMULSION, DRYING THE TREATED FIBERS UNDER CONDITIONS TO CAUSE THE HIGHER ORGANIC KETENE DIMER TO BECOME ATTACHED THERETO, APPLYING A SIZING MATERIAL SELECTED FROM THE GROUP CONSISTING OF ROSIN SIZE, WAX SIZE AND KETENE DIMER SIZE TO THE THUS TREATED FIBERS, AND DRYING AND HEATING THE THUS TREATED FIBERS TO DEVELOP SIZING. 